There will be no change in length if the line is viewed parallel to plane on which the line is present and also if the line is rotated with respect to perpendicular planes.

Projection of Lines topics include: Straight lines projection, line projection, line inclined projection with planes, straight line length and line traces. The projection of a line is a line or point on a plane. If a line is perpendicular to a plane, its projection is a point.  The projection of a line segment is the line segment formed by projecting the endpoints of the existing line segment on the new line.  The projection of an object is the figure or view formed by joining the points at which the lines meet the plane. The lines or rays drawn from the object to the plane are called... Show more

Projection of Lines topics include: Straight lines projection, line projection, line inclined projection with planes, straight line length and line traces.

The projection of a line is a line or point on a plane. If a line is perpendicular to a plane, its projection is a point. 

The projection of a line segment is the line segment formed by projecting the endpoints of the existing line segment on the new line. 
The projection of an object is the figure or view formed by joining the points at which the lines meet the plane. The lines or rays drawn from the object to the plane are called projectors. The transparent plane on which the projections are drawn is known as the plane of projection. 
Projection theory is based on two variables: line of sight (projecting lines) and plane of projection. A line of sight (LOS) is an imaginary line between an observer's eye and an object. A plane of projection is an imaginary flat plane upon which the image is projected.

Related Tests:

Engineering Drawing Practice Test: Projection of Points

Engineering Drawing Practice Test: Loci of Points & Orthographic Projections 

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